Biometrics is the study of signatures of a biological origin that can uniquely identify individuals. Biometric technology has increased in interest in recent years, and can be classified in two groups, cooperative identification and non-cooperative identification. Cooperative biometric identification methods obtain biometric readings with the individual's knowledge, and typically detect biological signatures such as finger prints, palm prints, and iris scans. Non-cooperative biometric identification methods obtain biometric readings without the person's knowledge, and typically detect facial, speech, and thermal signatures of an individual. This disclosure focuses on devices and methods that can detect various biometric signatures of both cooperative and non-cooperative individuals, through the use of imaging devices.
Facial and iris detection are some of the more common signatures used by security applications for identifying individuals. These methods of detection involve two independent steps, an enrollment phase where biometric data is collected and stored in a database and a query step, where unknown biometric data is compared to the database to identify the individual. In both of these steps, a camera can be used to collect and capture the images of the individual's face or iris. The images are processed using algorithms that deconstruct the image into a collection of mathematical vectors which, in aggregate, constitute a unique signature of that individual.
Digital imaging devices are often utilized to collect such image data. For example, charge-coupled devices (CCDs) are widely used in digital imaging, and have been later improved upon by complementary metal-oxide-semiconductor (CMOS) imagers having improved performance. Many traditional CMOS imagers utilize front side illumination (FSI). In such cases, electromagnetic radiation is incident upon the semiconductor surface containing the CMOS devices and circuits. Backside illumination CMOS imagers have also been used, and in many designs electromagnetic radiation is incident on the semiconductor surface opposite the CMOS devices and circuits.
As a major caveat to biometric signature acquisition, however, pigmentation of the skin and/or iris can affect the ability to collect robust data, both in the enrollment phase as well as in the future query phase. The pigmentation can mask or hide the unique structural elements that define the values of the signature mathematical vectors.